In an electrophotographic image forming apparatus, an electrostatic latent image formed on a surface of a photoreceptor is developed with toner by a developing device. The toner for use in the development of the electrostatic latent image is stored in a toner container (such as a toner cartridge or a toner bottle), and the toner is sequentially supplied from the toner container to the developing device.
Since high-speed image forming apparatuses consume a large amount of toner, the image forming apparatuses use capacious toner containers. Among the toner containers, rotary toner bottles have been conventionally used since the rotary toner bottles can control the discharge amount of toner with high precision. In many cases, such a toner bottle is formed so as to have a hollow cylindrical section, one end of which is closed and the other end of which has an outlet provided thereby. Further, such a toner bottle is mounted in an image forming apparatus so that the cylindrical section has a horizontal axis. Furthermore, some of such toner bottles have an inner circumferential surface provided with spiral protruding portions. When such a toner bottle is driven to rotate on its axis, the protruding portions provided on the inner circumferential surface convey toner while guiding the toner toward the outlet. As a result, an amount of toner corresponding to the rotation is discharged via the outlet.
In recent years, in order to reduce the power consumption of an image forming apparatus, an attempt to lower the melting point of toner has been made. This has caused a subtle change in fluidity of the toner, thereby making the toner likely to coagulate in a toner container. The likelihood becomes strong especially under hot and humid conditions. As a result, the toner coagulated in the toner container cannot be discharged successfully, and accumulates in the toner container. Finally, even though the toner remains in the toner container, the toner container is judged to be “out of toner”, a signal to replace the toner container is transmitted. This leaves no choice but “toner replacement” even though the toner has not been finished up. This brings about a very uneconomic situation.
As measures against such a situation, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 140908/2005 (Tokukai 2005-140908; published on Jun. 2, 2005)) and Patent Document 2 (Japanese Unexamined Patent Application Publication No. 71762/2006 (Tokukai 2006-71762; published on Mar. 16, 2006)) disclose a technique for forcibly preventing toner from coagulating, or for discharging coagulated toner, by providing a scraping member in a toner container.